Vibrato system for electrical musical instruments

ABSTRACT

In an electronic musical instrument including a tone generator, a vibrato signal generated by a vibrato oscillator is supplied to the tone generator together with a DC voltage proportional to the amplitude of the vibrato signal so as to cause the oscillation frequency of the tone generator to vary by a greater amount above the nominal frequency than below.

United States Patent VIBRATO SYSTEM FOR ELECTRICAL MUSICAL INSTRUMENTS 4 Claims, 5 Drawing Figs.

1.25, 1.01, (inquired); 331/178 [56] References Cited UNITED STATES PATENTS 2,466,306 4/1949 Daniel 84/l.25X 2,506,723 5/1950 Larson 84/1.25X 2,933,697 4/1960 Oncley 84/l.25X 3,083,606 5/1963 Bonham 84/1.25

Primary Examiner-Milton Or Hirshfield Assistant Examiner-Mark O. Budd Attorney-Holman, Glascock, Downing and Seebold ABSTRACT: In an electronic musical instrument including a tone generator, a vibrato signal generated by a vibrato oscillator is supplied to the tone generator together with a DC voltage proportional to the amplitude of the vibrato signal so as to cause the oscillation frequency of the tone generator to vary by a greater amount above the nominal frequency than below.

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M A-M VIBRATO SYSTEM FOR ELECTRICAL MUSICAL HNSTRUMENTS BACKGROUND OF THE INVENTION This invention relates to a novel vibrato system for electronic musical instruments.

As is well known in the art the vibrato effects utilized in playing musical instruments are provided by periodically varying the frequencies of musical tones above and below the nominal frequencies, but in playing prior electronic musical instruments, when the vibrato effects are utilized, auditors feel as if the tone pitches were lowered as a whole.

This is because that in prior electronic musical instruments utilizing the vibrato effects the frequency varies in a manner as indicated by a solid line curve a in FIG. 1 wherein the frequency varies substantially the same amplitude in both positive and negative directions with respect to the nominal tone pitch. It is considered that the tone pitch of the sounds accompanying the vibrato effect is felt by the auditors ears as the pitch of the center frequency minus the effective value of the frequency deviation rather than the center frequency (mean pitch) itself.

I have found that in almost all ordinary or nonelectrical musical instruments where the vibrato effect is utilized, the frequency varies such that the amplitude of the variation (amount of deviation) is greater in the direction above the nominal frequency than below.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide a novel vibrato system for electrical musical instruments, instruments wherein, where the vibrato effect is utilized, the frequency varies much more in the direction above the nominal frequency as in ordinary musical instruments.

According to this invention, in an electronic musical instrument including a tone generator, there' is provided a vibrato system comprising a vibrato oscillator to generate a vibrato signal, means to produce a direct current voltage proportional to the amplitude of the vibrato signal and means to supply the direct current voltage to the tone generator together with the vibrato signal so as to cause the oscillation frequency of the tone generator to vary much more in the direction above the nominal frequency.

Thus, the D.C. voltage acts as a bias voltage to resemble the vibrato effect provided by the electrical system to that of nonelectrical or ordinary musical instruments.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing:

FIG. 1 is a graph illustrating the vibrato effects provided by the system of this invention and by the prior art system;

FIG. 2 is a block diagram of one embodiment of the vibrato system embodying this invention;

FIG. 3 is a connection diagram of a modified embodiment of this invention;

FIG. 43 is an actual circuit of an a embodiment; and

FIG. 5 is an actual circuit of another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 2 illustrating one example of the novel vibrato system a vibrato oscillator l operates to generate a vibrato signal having a frequency (usually around 7 Hz.) and amplitude determined by a frequency and amplitude control device 2. The vibrato signal generated by the vibrato oscillator 1 is, on the one hand, rectified by a rectifier 3 to obtain a D.C. voltage having a value proportional to the amplitude of the vibrato signal, which is superposed upon the original vibrato signal in a mixer 4. Accordingly the superposed output signal from the mixer will vary around the level corresponding to the D.C. voltage. After being amplified by a D.C. amplifier S, the output signal is applied tothe vibrato input terminal of a tone generator 6 to cause its frequency toperiodically vary much more in the direction above the nominal frequency, thus introducing a vibrato effect similar to that of ordinary musical instruments into the oscillation frequency of the tone generator. To this end, the D.C. voltage produced by rectifying the vibrato signal is selected to have a polarity matched with the vibrato modulating characteristic of the tone generator. Thus, for example, the vibrato signal is rectified either positive or negative so that the frequency is shifted above when the D.C. voltage (absolute value) increases.

in the absence of the vibrato signal, since the signal applied to the vibrato input terminal of the tone generator contains no D.C. voltage (or only the inherent bias voltage), the oscillation frequency of the tone generator is adjusted to the nominal pitch under these conditions.

Dotted line curve b shown in FIG. 1 illustrates frequency variation of the vibrato effect provided by the novel system according to this invention. As can be noted from this curve the value of the D.C. voltage or the bias voltage is proportional to the amplitude of the vibrato signal so that the oscillation frequency of the tone generator changes much more in the direction above the nominal pitch than in the direction below it. In other words, the center frequency (mean pitch) is shifted higher by the amount proportional to the vibrato depth.

FIG. 3 shows a modified embodiment of this invention wherein a vibrato oscillator 11 controlled to generate a vibrato signal in the form of a symmetrical sine wave having a frequency of about 7 l-Iz., for example, is connected in series with a source of direct current voltage 12 acting as a bias source. The resultant of the vibrato signal and the D.C. bias, or the composit vibrato signal is applied across a variable resistor l3 and the composit vibrato signal of variable amplitude is supplied to the tone generator (see FIG. 1) through output terminals 15 to periodically vary the oscillation frequency of the tone generator..

Also in this embodiment, the polarity of the composit vibrato signal is matched with the vibrato modulating characteristics of the tone generator. More particularly, the tone generator is set such that to increase its oscillation frequency as the composit vibrato voltage is increased and that to oscillate at a predetermined pitch with the nominal frequency in the absence of the vibrato signal.

FIG. 4 shows an actual circuit of an embodiment of this invention. Numeral l designates a vibrato oscillator of a phaseshift type, numeral 2 designates a control of speed and depth, numeral 7 designates a device which produces a composit vibrato signal of an AC voltage plus a DC voltage proportional to the amplitude of said AC voltage, acting as the combination of the rectifier 3, the mixer 4 and the amplifier 5 of FIG. 2, and numeral 6 designates a tone generator.

The device 7 having above-mentioned faculty is very useful especially for a manually controlled vibrato system. FIG. 5 shows a circuit diagram of a system including a manually controlled vibrato signal generator 51 instead of the self-oscillator l of FIG. 4. The generator 53 produces a vibrato signal whose waveform is determined according to the variation of a variable resistor 52 (such as of CdS cell unit) by the manual operation thereof. This waveform is, generally, nonperiodic and irregular, but the final composit vibrato signal supplied to the tone generator contains a DC component proportional to the AC component due to the function of the device 51.

The result of experiment showed that when vibrato effect is applied to a tone of A, 440 Hz. satisfactory vibrato effect can be provided when the frequency varies 70 percent in the positive direction or above the nominal frequency and 30 percent in the negative direction or below the nominal frequency. In other words, the DC voltage is proportional to the AC voltage by the proportional coefficient of 0.2 (20 percent of the. peak-to-peak value of the AC voltage).

Thus, according to the vibrato system of this invention, since the frequency of the tone generator is shifted higher in proportion to the vibrato depth, it is possible to provide desirable vibrato characteristics substantially identical to those of ordinary of nonelectrical musical instruments. As a result, electronic musical instruments utilizing the novel vibrato system can manifest very comfortable vibrato effect.

I claim: I

l. A vibrato system for electronic musical instruments comprising a tone generator, a vibrato oscillator for generating a vibrato signal, means to generate a DC voltage proportional to the amplitude of said vibrato signal, and means to supply said DC voltage and said vibrato signal to said tone generator so as to cause the oscillation frequency thereof to vary much more in the direction above the nominal frequency than below.

2. The vibrato system according to claim 1 wherein said DC LII voltage is produced by a rectifier adapted to rectify the vibrato signal and the rectified DC voltage is supplied to said tone generator together with said vibrato signal.

3. The vibrato system according to claim 1 wherein said vibrato oscillator is connected in series with a source of fixed DC voltage and the resultant voltage is applied to said tone generator through a variable resistor.

4. The vibrato system according to claim 1 wherein the frequency of the tone generator varies 70 percent above and 30 percent below the nominal frequency. 

1. A vibrato system for electronic musical instruments comprising a tone generator, a vibrato oscillator for generating a vibrato signal, means to generate a DC voltage proportional to the amplitude of said vibrato signal, and means to supply said DC voltage and said vibrato signal to said tone generator so as to cause the oscillation frequency thereof to vary much more in the direction above the nominal frequency than below.
 2. The vibrato system according to claim 1 wherein said DC voltage is produced by a rectifier adapted to rectify the vibrato signal and the rectified DC voltage is supplied to said tone generator together with said vibrato signal.
 3. The vibrato system according to claim 1 wherein said vibrato oscillator is connected in series with a source of fixed DC voltage and the resultant voltage is applied to said tone generator through a variable resistor.
 4. The vibrato system according to claim 1 wherein the frequency of the tone generator varies 70 percent above and 30 percent below the nominal frequency. 